23
2025
-
06
Binary optics and metasurface lenses
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Binary Optics It can be considered a discipline or a type of optical technology; Meta-lens The concept is more inclined to be a device.
Their working principle is based on Diffractive optics Unlike previous imaging lenses, prisms, and some optical principles based on refraction or reflection.
The emergence of binary optics is largely due to the development of computer technology and micro-nano processing technology. Compared with traditional optical refractive devices, Binary optical elements are thin, small, and lightweight and can be obtained through replication methods.
Holographic optical elements, especially computational holography are of great significance to the development of binary optics. It is generally believed that the phase hologram is an early binary optical element. Regarding why this technology is called binary optics, a book titled "Binary Optics" provides the following description: Binary optics was proposed by a research group led by Veldkamp at MIT Lincoln Laboratory in the United States. Veldkamp said: "Now there is a branch of optics that is almost completely different from the traditional manufacturing method, which is diffractive optics, whose optical elements have a relief structure on the surface; because the production method used is originally used to produce integrated circuits, the mask used is binary. And the mask is layered in binary encoding form, so the concept of binary optics is introduced."
The above aptly explains the origin of the concept of binary optics.
A binary optical element is actually a pure phase diffractive element , which uses two or more heights of relief structures to perform a staircase approximation of the element's phase.
The diffraction efficiency of this type of device can generally be obtained according to this formula, which is the quantization order of the phase.
According to the literature I have read, it seems that the binary optics developed since the 1990s mainly studied relief structures larger than the wavelength unit, and the device design mainly relied on scalar diffraction theory, with a lot of work related to beam shaping. At that time, much of the research on binary optics focused on the construction of phase inversion algorithms, because the design of binary optical elements is an inverse diffraction problem , solving the transmission function of the diffraction screen based on the incident light field and the target diffraction field. This direction is very active, and I think it is also closely related to the development of computers.
In short, binary optical elements mostly consider the construction of axial relief structure size, using multi-stage structures to construct diffractive elements, This is different from the later metasurfaces, which mostly consider the construction of vertical axial structure size . Moreover, the development of metasurfaces also benefits from the development of optical theory, proposing many different phase mutation methods, Metasurfaces mostly study subwavelength periodic structural units 。
There is no essential difference between these two devices. Looking at the development of previous diffractive elements, as well as the design of superwavelength or subwavelength diffractive elements, and the design of harmonic diffraction achromatic devices, it seems that we can see the shadow of current metasurface research.
However, one difference is that current research on optical micro-nano structures combines solid-state physics, electronics, and other multidisciplinary crossovers , which is richer than the research on previous diffractive elements.
If you are interested in binary optics, you can refer to these two books.
As for metalenses, here is a copy of a previous article: Knowledge Notes | Superlens and Metalens 。
Currently, Superlens and Metalens are both called Superlens/Metalens , but they come from different research directions or research ideas.
Superlens is a metamaterial that can achieve super-resolution imaging. Its research ideas mainly come from researchers' research on "left-handed materials." , which is a material with negative permittivity and permeability. Pendry, J. B. theoretically analyzed the possibility of imaging of this material in 2000 and provided relevant proof that a negative refractive index plate can be used as a "perfect lens."
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